Bro, if you feel you need to be on an anti-d, weight gain should be the least of your concerns.
I tried four different anti-d's in combination with other drugs before I found the cocktail that finally worked for me. That cocktail saved my life.
If I had allowed weight gain to be of any consideration when making my choice, I would likely be dead by now.
Fuck worrying about weigh gain. Worry instead about getting mentally healthy.
Very best of luck.